(1.) Field of the Invention
The present invention relates to a method of manufacturing a gas barrier film using a capacitively coupled plasma-enhanced chemical vapor deposition (CVD) technique.
(2.) Description of the Related Art
Gas barrier films having a silicon nitride film formed on the surface of a resin (plastic) film are known as gas (water vapor) barrier films employed in various apparatuses and optical devices which are required to be moisture-proof.
Capacitively coupled plasma chemical vapor deposition (hereinafter abbreviated as “CCP-CVD”) is known as a process for forming a silicon nitride film.
As is well known, CCP-CVD is a technique in which a gaseous raw material is supplied between a deployed pair of electrodes, and a voltage is applied to generate plasma, which causes the gaseous raw material to dissociate and ionize to generate radicals and ions, thus performing film formation by means of plasma CVD on the surface of an object disposed between the electrodes.
The CCP-CVD method is advantageous in that, because the gaseous raw material is supplied from the electrodes in a simple structure, gas can be uniformly supplied to the whole film-forming area (gas is easily made uniform) even in the case where the electrodes have an increased surface area, and hence this technique can be easily applied to a substrate having a large surface area.
For example, JP 2009-179874 A discloses a method of forming a gas barrier layer having a ratio P/Q of 0.4 to 40, when the RF power required to form a silicon nitride film is P (W), and the total flow rate of silane gas, ammonia gas, and nitrogen gas is Q (sccm).
In the method disclosed in JP 2009-179874 A, a silicon nitride film having excellent gas barrier properties can be produced at a high film formation rate by setting the ratio P/Q to 0.4 to 40 and increasing the RF power per the total flow rate of the gases.
When producing a gas barrier layer, the roll-to-roll film-forming method is generally known as being an efficient method for forming a film on a substrate while ensuring high productivity.
The roll-to-roll film formation apparatus continuously forms a film on a substrate in the film formation chamber while synchronously feeding the substrate from the feed roll to the take-up roll along a predetermined pathway extending from the feed roll upon which the lengthy substrate (web-shaped substrate) is wound in a roll-shaped manner, to the take-up roll upon which the substrate is subsequently wound in a roll-shaped manner after passing through the film formation chamber where the film is formed on the substrate.
However, the substrate may be softened by the large amount of heat applied to the substrate during the film formation when the RF power per gas flow rate is increased to form a silicon nitride film with excellent gas barrier properties at a high film formation rate, as described in JP 2009-179874 A. Therefore, the softened substrate is susceptible to deformation by the load applied to the substrate during feeding, thus causing damage to the silicon nitride film formed on the substrate and degrading the gas barrier properties when forming a film under high power using the roll-to-roll method, as in the method disclosed in JP 2009-179874 A.
An object of the present invention is to solve the above-mentioned problems of the prior art by providing a method of manufacturing a gas barrier film capable of forming a silicon nitride film having excellent gas barrier properties with high productivity, and reducing deformation of the substrate when feeding the substrate, even when RF power per gas total flow rate is increased to improve productivity and gas barrier properties, when forming a silicon nitride film on a substrate by means of capacitively coupled plasma CVD while feeding the lengthy substrate in the longitudinal direction.